The present invention relates generally to antennas, and more particularly to compact circularly-polarized antennas with expanded frequency bandwidth.
A wide range of consumer, commercial, industrial, and military applications utilize global navigation satellite systems (GNSSs), such as the Global Positioning System (GPS), for precision timing and location measurements. For specific applications, a variety of GPS receivers are available. A key component of a GPS receiver is the antenna, which is designed to meet user-specified mechanical and electromagnetic specifications. Mechanical specifications include size, weight, and form factor. Electromagnetic specifications include resonant frequency, bandwidth, sensitivity, gain, antenna pattern, and polarization. Cost and ease of manufacturing are also important considerations in antenna design.
One example of an adaptive antenna for detecting circularly-polarized radiation is described in U.S. Pat. No. 6,618,016. It can be dynamically programmed for multiple antenna patterns. This versatility is achieved, however, with a mechanically complex, eight-element design and a complicated excitation system. For some applications, furthermore, the bandwidth and azimuthal uniformity of the antenna pattern are not adequate.
What is needed is a light weight, compact antenna that receives circularly-polarized radiation, has low sensitivity to multipath reception, has a high bandwidth, and has an azimuthally-uniform antenna pattern. An antenna that is easy to manufacture at low cost is desirable.